Tree Wells

Tree Wells infiltrate stormwater runoff into the soil immediately surrounding a planted tree. Generally, the areas around the Tree Well are sloped to allow water to naturally flow into the Tree Well. After rainfall, runoff collected in the Tree Well infiltrates into the soil, capturing pollutants that would otherwise enter our local creeks and rivers..

Tree Wells also reduce the volume of runoff entering the storm drain system and can prevent surface floods. Tree Wells are often found adjacent to walkways, driveways, and parking areas to capture and treat stormwater runoff flowing from these surfaces.

Benefits

Tree Wells may offer the following benefits:
 

• Interception of rainfall: Tree surfaces, including roots, foliage, bark, and branches, play a vital role in managing precipitation by intercepting, evaporating, storing, or channeling it to the soil, reducing the amount that reaches surrounding impervious surfaces (paved or hard surfaces).
• Reduced erosion: Trees help protect exposed areas by intercepting rainfall and slowing down the velocity of raindrops as they pass through the tree canopy, minimizing soil disturbance.
• Increased infiltration: Tree roots and fallen leaves improve soil structure, creating conditions that enhance water infiltration into the ground.
• Treatment of storm water: Trees contribute to stormwater treatment by absorbing nutrients and other pollutants, while also supporting biological processes that break down pollutants.
  
  

What does your Tree Well look like?

Typical Tree Wells configuration can include:

1. Runoff Flow Path: Guides stormwater into the tree well for treatment and infiltration.
2. Inlet Area: The entry point for stormwater, which can include curb cuts, grates, or other structures.
3. Surface Ponding Area: A shallow depression designed to temporarily hold stormwater before it infiltrates into the soil.
4. Mulch Layer: A specified number of inches of mulch to retain moisture, reduce erosion, and support tree health.
5. Tree Well Soil Media: Specially engineered soil that promotes infiltration, nutrient uptake, and pollutant removal.
6. Underdrain (if required): A drainage system beneath the soil media to manage excess water in areas with poor infiltration rates.
    

Target Pollutants

• Sediment (soils particles, road dust, gravel, sand, etc.)
• Trash
• Debris
   

Inspection & Maintenance Activities

BMP Fact Sheets in PDF format

Structural BMP Outreach Flyers (Educational Resources Page)
 

Contact

  (858) 495-5323

  BMP.Program@sdcounty.ca.gov

Maintaining My Structural BMP Home Page